Richard Manning: “Against The Grain”Posted: August 1, 2011
“The effects of modern industrial agriculture range from pesticide pollution to freshwater depletion, energy consumption, erosion, and salinization. We can, nevertheless, trace the Green Revolution’s swath across the planet, especially in marine systems, by focusing on a single element – nitrogen. Beginning in about 1950, the use of nitrogen fertilizer ballooned from less than five million tons annually worldwide to about eighty million tons today….
Most of the nitrogen leaves farm fields with runoff, so the most apparent damage is to rivers, wetlands, estuaries, and seas where it causes eutrophication, anoxia, and hypoxia, various types of oxygen depletion as a result of excess nitrogen. Dots of these water-borne problems pock the globe, wherever farming touches water, but the problem is most easily read in the Gulf of Mexico, which now bears a twenty-thousand square-kilometer hypoxic Dead Zone. Fish and shrimp have disappeared from this area; 85 percent of the gulf’s estuaries are affected. The nitrogen causing this all comes from the Mississippi River, which drains a vast region of the United States, but an Army Corps of Engineers study was quite specific about the source. Seventy percent of the Mississippi’s nitrogen comes from a relatively small six-state area that is the heart of the nation’s corn belt.”